1. Field of the Invention
The present invention relates to signaling information in communication systems or networks supporting Broadcast-Multicast services (BCMCS).
2. Related Art
Current second generation and third generation wireless systems are primarily designed to support unicast voice and data services. The support of these unicast services to the end user has been achieved through various advances in wireless and networking technologies. The current emphasis in international standardization bodies such as 3GPP and 3GPP2 is on the design of protocols and procedures that allow the support of Broadcast-Multicast Services (BCMCS) over evolving networks. BCMCS is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to a large number of recipients. Examples of these services include voice dispatch or Press-To-Talk (PTT) type services, broadcast/multicast streaming, etc.
There has been recent industry interest in the Public Safety Wireless Network (PSWN) context, where support of BCMCS may be especially important in terms of radio resource management. Radio resource management procedures may be needed to achieve low delay in establishment and delivery of BCMCS content, to provide scalability in terms of the number of multicast groups and/or number of users per multicast group, and to provide advanced service capabilities (e.g., ability to monitor/extract content from multiple BCMCS streams). Further, radio resource management procedures may be needed to achieve high spectral efficiency, to provide security (authentication, encryption and identity protection), and to improve mobile station battery life. Thus, radio resource management procedures that improve spectral efficiency, battery life and/or provide service flexibility are of interest to network operators.
Thus, new technical challenges are emerging in the design of radio resource management procedures to improve spectral efficiency and service flexibility in third generation wireless communication systems providing mixed voice and data services. In meeting mixed voice and data service demands, system overhead information should be carried for signaling BCMCS streams, or flows. This system information may be embodied as a radio channel configuration, logical to physical channel mappings, neighbor list information, etc, for example.
A message referred to as a Broadcast Service Parameters Message (BSPM) carries this BCMCS-related signaling information. The size of the BSPM depends on factors such as the number of Broadcast-Multicast (BCMC) sessions for which logical-to-physical mappings (LPMs) have been established in the sector. An LPM specifies which BCMCS content is carried by what physical channel (such as a Forward Broadcast Supplemental Channel (F-BSCH) in cdma2000, for example) in the forward link. The BSPM may possibly be several hundreds of bytes long. The timely delivery of BSPM may require data rates on the order of several kbps.
A necessity exists to design and define efficient methods for carrying the BSPM that enable delivery of ‘time-critical’ BSPMs with low delays, so as to provide quick notification of availability of BCMC content for a BSPM flow and/or quick initiation of content delivery for a certain BCMC flow. In addition, the BSPM should use spectrally efficient channels for transmission and should not significantly impact battery life of BCMC-capable mobile stations. Further, the BSPM (and transmission thereof) should minimize impact on battery life of mobile stations that do not have BCMC capabilities.
Current techniques for transmission of the BSPM in third generation wireless communications networks such as cdma2000 3G.1x include use of a paging channel (PCH) and/or a Forward Common Control Channel/Forward Broadcast Control Channel (F-CCCH/F-BCCH). In third generation wireless communications networks such as cdma2000 3G.1x spread spectrum systems, a PCH is a code channel in a Forward CDMA Channel that is used for transmission of control information and pages from a base station to a mobile station. A paging channel slot may be defined as an 80 ms interval on the PCH. Mobile stations operating in the slotted mode are assigned specific slots in which they monitor messages from the base station. Mobile stations in an idle state and operating in slotted mode only monitor selected slots on the PCH and F-CCCH, thereby improving battery life.
A feature known as ‘Quick Paging’ permits mobile stations to further conserve battery power beyond the savings achieved by slotted mode operation. A Quick Paging Channel (QPCH) is an un-coded, on-off-keyed (OOK) spread spectrum signal sent by base stations to inform slotted mode mobile stations, operating in the idle state, whether to monitor the PCH or the Forward Common Control Channel (F-CCCH). Like the PCH, the QPCH has an 80 ms duration. A paging indicator is a one-bit datum sent on the QPCH. Quick paging indicators are associated with mobile stations, in pairs, via a hashing algorithm. Appearance of both of its paging indicators in its assigned QPCH slot serves to alert a slotted mode mobile station, operating in the idle state, that the mobile should monitor the PCH or the F-CCCH starting in the next slot.
In general, the PCH technique involves paging to indicate BSPM changes, and paging to indicate what BSPMs are transmitted on the PCH. For BSPM transmission on the PCH, data rates are relatively low (up to only about 9.6 kbps). In addition, there exists low spectral efficiency, which is inefficient for transmitting long BSPMs in a timely manner.
Currently, PCH protocol provides two methods for the transmission of broadcast messages, (a) Multi-slot Broadcast Message Transmission; and (b) Periodic Broadcast Paging. Each method enables mobile stations operating in the slotted mode or in the non-slotted mode [define as compared to slotted mode] to receive broadcast messages. According to (a), a broadcast message is sent in a sufficient number of assigned slots such that it may be received by all mobile stations that are operating in the slotted mode. Thus, a BSPM transmission appears on all assigned slots in a slot cycle, which may result in an inefficient use of forward link resources.
According to (b), mobile stations configured to receive broadcast messages monitor a specific broadcast slot, such as the first slot of a broadcast paging cycle. If all of the broadcast messages to be transmitted fit within the first slot of a broadcast paging cycle, they may all be transmitted in this broadcast slot. If there is a single broadcast message to be transmitted, the single broadcast message may be transmitted at the beginning of this broadcast slot.
Alternately, one or more broadcast pages may be transmitted in the first slot of a broadcast paging cycle. Each broadcast page is associated with a subsequent broadcast slot. For each broadcast page, an associated broadcast message may be transmitted in the associated subsequent broadcast slot. A problem with (b) is that a non-BCMC capable mobile station that supports the QPCH will “wake up” to decode BSPM. This method thus may waste battery life of these non-BCMC capable mobile stations.
For transmitting a BSPM on a F-CCCH, paging on the F-CCCH is used to inform slotted mode mobiles of the BSPM transmission, and the F-BCCH is used to carry the BSPM. One method available for paging on the F-CCCH is use of a multi-slot enhanced broadcast page. However, this method has the same problem as the Multi-slot Broadcast Message Transmission for PCH. Namely, a BSPM transmission appears on all assigned slots in a slot cycle, which may result in inefficient use of forward link resources.
Another method for BSPM transmission on the F-CCCH includes use of a periodic enhanced broadcast page. However, this method has a problem similar to the Periodic Broadcast Paging described with respect to the PCH. In other words, the same battery life problem for mobile stations that do not support BCMCS exists. Additionally, there exists a minimum broadcast paging cycle of 5.12 seconds, which may adversely affect a delay requirement for delivery of “time-critical” BSPMs. Further, frequent changes in BSPM information technology may also require legacy mobile stations to monitor the F-BCCH, even though there have been no changes in other system information (unrelated to BCMCS).